The influence and reason analysis of the vanishing twin on noninvasive prenatal testing

Objective To investigate the influence and reason analysis of the vanishing twin on noninvasive prenatal testing. Methods Clinical data of the pregnant women with vanishing twin syndrome (VTS) who came to our department for NIPT from January 2019 to December 2023 were collected, and their general conditions, NIPT results and prenatal diagnosis results as well as the causes of test failure were analyzed. The effects of gestational week of VTS and re-sampling time slot on the positive rate of NIPT were also discussed. Results Of the 102 cases, 5 cases were NIPT positive (4.9%), among them 4 cases were sex chromosome abnormality (SCA), and 1 case was ChrX-(Z=-7.38), that is, X chromosome reduction. The karyotype and CNV-seq results were all normal after amniocentesis. Namely, all the 5 cases were false positive, and the rate was 100% (5/5). The positive rate of VT < 10 weeks (3/73) was lower than that of VT ≥10 weeks (2/29). There was no significant difference in positive rate between the two groups. (P > 0.05) Conclusion NIPT could be applied on VT pregnancy, prolong the time interval of fetal demise and NIPT sampling. Once established, unnecessary invasive procedures could be avoided, mitigating negative emotional impact on future mothers.